It is our objective to obtain information on ligand-heme protein interactions by studying the kinetics and spectral changes triggered by the photoexcitation of heme proteins. Many of the key chemical and physical processes following photoexcitation, such as energy relaxation, ligand dissociation, cage recombination, and tertiary changes, occur in the subnanosecond time domain. The use of picosecond laser method provides the time resolution necessary to study these phenomena. Kinetics and transient spectral data will be obtained using picosecond transient absorption spectroscopy (which we have already initiated) and Raman spectral data from picosecond coherent anti-Stokes Raman scattering. The experiments that we have initiated and propose seek to determine the role of a number of variables: specific bound ligand, degree of photolysis, excitation wavelength, solvent variables such as pH and bound phosphate, and number of heme groups, on the kinetics of energy decay, ligant photodissociation, cage recombination, and tertiary structural changes in a number of heme proteins. The health related implications of the work include: interactions of heme proteins with biological important ligands, e.g. O2 and CO, effects of organic phosphates present in blood on heme proteins, and the nature of energy degrading pathways which can help in understanding the effects of radiation exposure on the heme proteins.